friends :im planning to join a personla trainers course in exercise and nutrition , so can any one of u suggest me which is the best?i heard about ISSA/ACE/ACSM?what do u say?

ISSA is pretty good. As is NASM, NSCA, and ACSM. I would avoid ACE, because IMO much of their curriculum sucks. The nice thing about ACE though, is that it's a very widely recognized certification. You won't have any trouble finding a job with that certification.

If you don't have any formal education in exercise science, physiology, or kinesiology, I wouldn't even bother looking at the ACSM. They're known as the premier certifying organization, and if I remember correctly, you MUST have a related degree to even sit for the test.